The present invention generally relates to a magnetically operated actuator and, more particularly, to the magnetically operated actuator suited for actuating an operating element such as used in, for example, a photographic shutter mechanism, a photographic aperture mechanism, a high speed on-off electric switch or any other machine component which required to be operated in response to the application of an electric enabling signal.
A magnetically operated actuator utilizing a combination of electromagnet and permanent magnet is currently commercially available, wherein the magnetic forces produced respectively by the electromagnet and the permanent magnet interact with each other to drive an operating element for, for example actuating a switch contact used in a control circuit. The prior art magnetically operated actuator is generally so designed as to make use of the opposite polarities, induced in the electromagnet when the latter is electrically energized, in actuating the operating element, that is, as to establish a closed magnetic circuit between the electromagnet and the permanent magnet.
When it comes to the utilization of the opposite polarities induced in the electromagnet for the purpose of actuating the operating element, it has been found difficult to proportionate the magnetic force emanating between the opposite poles of the electromagnet with the magnetic force of the permanent magnet coupled with the operating element and, therefore, the drive produced by the magnetically operated actuator as a whole tends to become insecure.
Moreover, although it seems that the drive produced by the magnetically operated actuator will theoretically double when the opposite poles of the electromagnet is utilized as compared with the case when only one of the opposite poles thereof is utilized, the fact is that the drive produced by the magnetically operated actuator as a whole tends to be cut by half because the proportionated relationship between the magnetic forces produced respectively by the electromagnet and the permanent magnet fails to sustain itself with the result that the magnetic force of attraction produced by one of the electromagnet and the permanent magnet will not match with the magnetic force of repulsion produced by the other of the electromagnet and the permanent magnet.
In addition, in the prior art magnetically operated actuator now under discussion, since at least one of the opposite polarities produced in the electromagnet must be magnetically conducted to a position at which it is actually utilized, the use of a relatively bulky iron core in the electromagnet is necessitated and/or the magnetically operated actuator itself tends to become complicated in structure to such an extent as to result in the deviation in performance from one actuator to another during the manufacture thereof.
Furthermore, since during the operation of the magnetically operated actuator the operating element is brought into contact with any one of the opposite poles of the electromagnet, the operating element is susceptible to the built-up of residual magnetism which will constitute a cause of reduction in response of the operating element to the application of an electric signal.